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Bend Allowance Calculator (Online & Free)

Have you ever struggled with calculating the right bend allowance for your sheet metal projects? In this blog post, we’ll dive into the world of bend allowances and explore how to use a bend allowance calculator to streamline your workflow. As an experienced mechanical engineer, I’ll share my insights and break down the concepts behind this handy tool. Get ready to learn how to achieve precise bends and save time on your next project!

Bend Allowance Calculator

Table Of Contents

For new press brake operators who may not be familiar with the intricacies of calculating bend allowance, a bend allowance calculator can be an invaluable tool. This calculator simplifies the process, ensuring accurate results and making daily work more efficient.

I. Bend Allowance Calculator

Parameters Required for Calculation

To use the bend allowance calculator effectively, operators need to input the following parameters:

  1. Material Thickness: The thickness of the material influences the bend radius and the overall bend allowance.
  2. Inside Radius: The radius of the bend on the inside surface of the material.
  3. K-Factor: A ratio that helps determine the location of the neutral axis during bending.
  4. Bend Angle: The angle at which the material is bent.

Related calculator:

Further reading:

II. What Is Bend Allowance?

Bend allowance is the additional material length required when bending sheet metal to achieve the desired final dimensions after forming. It compensates for the stretching and compression that occurs in the material during the bending process.The bend allowance varies based on several factors:

  1. Material properties: Different materials have different elasticity and plasticity, which affect how much the material stretches or compresses during bending.
  2. Sheet thickness: Thicker sheets generally require a larger bend allowance compared to thinner sheets of the same material.
  3. Bending method and tooling: The type of bending process (e.g., air bending, bottoming, coining) and the design of the bending die can influence the bend allowance.
  4. Inside bend radius: A tighter inside bend radius typically requires a smaller bend allowance than a larger radius.

Bend allowance values are typically determined through a combination of empirical data, mathematical calculations, and practical experience. Experienced sheet metal designers and engineers have developed bend allowance tables and formulas over years of repeated testing and verification.

By using the appropriate bend allowance formula or referring to reliable bend allowance charts, designers can accurately calculate the flat pattern dimensions of a sheet metal part that will yield the desired final bent dimensions. This is crucial for creating accurate flat patterns and ensuring that the bent part fits and functions as intended.

III. Bend Allowance Formula

Bend allowance and bend deduction calculations are essential methods used to determine the length of sheet metal raw materials in their flat form, ensuring the desired size of the bent part is achieved. Understanding these calculations is crucial for precision in sheet metal fabrication.

Bend Allowance Calculation Method:

The bend allowance (BA) is the amount of material that is added to the total length of the flat sheet to account for the material that will be used in the bend. 

The following equation is used to determine the total flattening length when the bend allowance value is used:

Lt = A + B + BA

Where:

  • 𝐿𝑡 is the total flat length.
  • 𝐴 and 𝐵 are the lengths of the two straight sections of the sheet metal before the bend (as shown in the figure).
  • 𝐵𝐴 is the bend allowance value.

Bend Deduction Calculation Method:

The bend deduction (BD) is the amount of material that is subtracted from the total length of the flat sheet to account for the material that will be used in the bend. 

The following equation is used to determine the total flattening length when using the bend deduction value:

Lt = A + B – BD

Where:

  • 𝐿𝑡 is the total flat length.
  • 𝐴 and 𝐵 are the lengths of the two straight sections of the sheet metal before the bend (as shown in the figure).
  • 𝐵𝐷 is the bend deduction value.

Other Calculation Methods

In addition to the bend allowance and bend deduction methods, other techniques can be used to determine the flat length of sheet metal raw materials. These include:

  • Bending Allowance Chart: A pre-calculated chart that provides bend allowance values for various materials and bend angles.
  • K-Factor: A ratio that represents the location of the neutral axis relative to the thickness of the material. It is used in more precise bending calculations.
  • Bending Calculations: These involve more complex formulas and considerations, such as material properties, bend radius, and thickness, to achieve accurate results.

IV. Bend Allowance Chart

1. Bend allowance chart for SPCC (mild steel)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SPCC0.590V40.50.95
1000.73
1350.3
1750.03
  
SPCC0.590V50.51.03
1000.79
1350.33
1750.03
  
SPCC0.590V60.51.1
1000.85
1350.35
1750.03
  
SPCC0.690V40.51.08
1000.83
1350.35
1750.03
  
SPCC0.690V50.51.15
1000.89
1350.37
1750.03
  
SPCC0.690V60.51.23
1000.95
1350.39
1750.03
  
SPCC0.890V60.51.49
1200.73
1350.47
1500.25
  
SPCC0.890V801.64
1200.81
1350.52
1500.27
  
SPCC0.890V1001.79
1200.88
1350.57
1500.3
  
SPCC190V1002.05
1001.58
1201.01
1350.62
1750.06
SPCC190V801.9
1001.47
1200.93
1350.6
1750.05
SPCC190V601.74
1001.35
1200.86
1350.56
1750.05
SPCC1.290V101.42.31
1001.78
1201.13
1350.73
1750.06
SPCC1.290V81.42.15
1001.66
1201.06
1350.69
1750.06
SPCC1.290V61.42
1001.55
1200.98
1350.64
1750.05
SPCC1.590V61.72.36
1001.82
1201.16
1350.75
1750.06
SPCC1.590V121.72.8
1002.17
1201.38
1350.89
1750.08
SPCC1.590V101.72.65
1002.05
1201.31
1350.85
1750.07
SPCC1.590V81.72.5
1001.94
1201.23
1350.8
1750.07
SPCC290V1023.29
1002.54
1201.62
1351.05
1750.09
SPCC290V1223.44
1002.66
1201.69
1351.1
1750.09
SPCC2.590V183.034.6
1003.56
1202.26
1351.47
1750.12
SPCC2.590V123.034.15
1003.21
1202.04
1351.32
1750.11
SPCC2.590V103.034
1003.09
1201.97
1351.28
1750.11
SPCC390V183.133.135.22
1004.03
1202.57
1351.66
1750.14
SPCC390V123.134.78
1003.69
1202.35
1351.52
1750.13
SPCC390V103.134.63
1003.58
1202.28
1351.48
1750.13

2. Bend allowance chart for SUS (stainless steel)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SUS0.59040.61.04
1000.79
1200.48
1350.3
1750.04
SUS0.59050.61.15
1000.88
1200.54
1350.33
1750.04
SUS0.59060.61.27
1001.13
1200.59
1350.37
1750.04
SUS0.69040.61.16
1000.88
1200.54
1350.34
1750.04
SUS0.69050.61.27
1000.97
1200.59
1350.37
1750.04
SUS0.69060.61.38
1001.05
1200.64
1350.4
1750.05
SUS0.89041.11.4
1001.06
1200.65
1350.4
1750.05
SUS0.89051.11.51
1001.15
1200.7
1350.44
1750.05
SUS0.89061.11.62
1001.23
1200.75
1350.47
1750.06
SUS19061.91.87
1001.42
1200.87
1350.54
1750.07
SUS19081.92.1
1001.6
1200.98
1350.61
1750.07
SUS1.29061.62.1
1001.59
1200.97
1350.61
1750.07
SUS1.29081.62.32
1001.76
1201.08
1350.67
1750.08
SUS1.290101.62.54
1001.93
1201.18
1350.74
1750.09
SUS1.59082.12.68
1002.03
1201.24
1350.77
1750.09
SUS1.590102.12.9
1002.2
1201.35
1350.84
1750.1
SUS29010 3.49
1002.65
1201.62
1351.01
1750.12
SUS29012 3.7
1002.82
1201.72
1351.07
1750.13

3. Bend allowance chart for SPHC (stainless steel)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SPHC190V101.862.05
1001.58
1201.01
1350.62
1750.06
SPHC190V81.861.9
1001.47
1200.93
1350.6
1750.05
SPHC190V61.861.74
1001.35
1200.86
1350.56
1750.05
SPHC1.290V101.442.31
1001.78
1201.13
1350.73
1750.06
SPHC1.290V81.442.15
1001.66
1201.06
1350.69
1750.06
SPHC1.290V61.442
1001.55
1200.98
1350.64
1750.05
SPHC1.590V121.742.8
1002.17
1201.38
1350.89
1750.08
SPHC1.590V101.742.65
1002.05
1201.31
1350.85
1750.07
SPHC1.590V81.742.5
1001.94
1201.23
1350.8
1750.07
SPHC290V122.013.44
1002.66
1201.69
1351.1
1750.09
SPHC290V102.013.29
1002.54
1201.62
1351.05
1750.09
SPHC2.590V1834.6
1003.25
1202.26
1351.47
1750.12
SPHC2.590V1234.15
1003.21
1202.04
1351.32
1750.11
SPHC2.590V1034
1003.09
1201.97
1351.28
1750.11
SPHC390V183.15.22
1004.03
1202.57
1351.66
1750.14
SPHC390V123.14.78
1003.69
1202.35
1351.52
1750.13
SPHC390V103.14.63
1003.58
1202.28
1351.48
1750.13

4. Bend allowance chart for SECC (galvanized steel sheet)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SECC190V101.92.05
1001.58
1201.01
1350.62
1750.06
SECC190V81.91.9
1001.47
1200.93
1350.6
1750.05
SECC190V61.91.74
1001.35
1200.86
1350.56
1750.05
SECC1.290V101.42.31
1001.78
1201.13
1350.73
1750.06
SECC1.290V81.42.15
1001.66
1201.06
1350.69
1750.06
SECC1.290V61.42
1001.55
1200.98
1350.64
1750.05
SECC1.590V121.72.8
1002.17
1201.38
1350.89
1750.08
SECC1.590V101.72.65
1002.05
1201.31
1350.85
1750.07
SECC1.590V81.72.5
1001.94
1201.23
1350.8
1750.07
SECC290V1223.44
1002.66
1201.69
1351.1
1750.09
SECC290V1023.29
1002.54
1201.62
1351.05
1750.09
SECC2.590V183.034.6
1003.56
1202.26
1351.47
1750.12
SECC2.590V123.034.15
1003.21
1202.01
1351.32
1750.11
SECC2.590V103.034
1003.09
1201.97
1351.28
1750.11
SECC390V183.135.22
1004.03
1202.57
1351.66
1750.14
SECC390V123.131.78
1003.69
1202.35
1351.52
1750.13
SECC390V103.134.63
1003.58
1202.28
1351.48
1750.13

5. Bend allowance chart for aluminum plate

MaterialThicknessBending angleV openingInner radiusBends Allowance
AL0.89040.61.15
1000.81
1200.5
1350.36
1750.03
AL0.89050.61.2
1000.85
1200.52
1350.37
1750.03
AL0.89060.61.25
1000.88
1200.54
1350.39
1750.03
AL19060.61.49
1001.05
1206.5
1350.46
1750.04
AL19080.61.59
1001.13
1200.69
1350.5
1750.04
AL1.29060.91.73
1001.22
1200.75
1350.54
1750.04
AL1.29080.91.82
1001.29
1200.79
1350.57
1750.05
AL1.59081.22.18
1001.54
1200.95
1350.68
1750.06
AL1.590101.22.28
1001.61
1200.99
1350.71
1750.06
AL1.590121.22.38
1001.68
1201.03
1350.74
1750.06
AL290141.63.07
1002.17
1201.3
1350.93
1750.08
AL290121.62.98
1002.11
1201.34
1350.95
1750.08
AL290181.63.25
1002.3
1201.42
1351.01
1750.08
AL2.590182.43.89
1002.75
1201.7
1351.21
1750.1
AL390182.54.5
1003.18
1201.96
1351.4
1750.1
AL3.290182.54.74
1003.35
1202.06
1351.47
1750.12
AL490404.66.77
1004.79
1202.95
1352.11
1750.17
AL6.8908009.412.09
1008.55
1205.27
1353.76
1750.31

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Shane
Author

Shane

Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

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